This invention relates to the formation of fragile parts of changing cross sections, which have been difficult to manufacture, it being a primary object of this invention to provide securement means by which work is firmly held for removal of material. Heretofore, work pieces have been held by chucks, vices or clamps, etc. and they have been cemented in place for machining. Also, ferrous work pieces have been secured to magnetic chucks while non ferrous work pieces have been secured to vacuum chucks, etc. Because of the difficulty in securement of fragile work pieces, resort has been made to tedious methods of material removal such as chemical milling and electrical discharge milling etc. Furthermore, accuracy of material removal remains a problem even with the aforesaid high tech methods of material removal, it being an object of this invention to provide a machining method and apparatus by which material is removed with extreme facility and accuracy. With the present invention accuracy is inherent so that precision parts are produced economically.
The parts manufactured by this method and apparatus vary widely in material kind and configuration. That is, the material can be ferrous or non ferrous, metallic or non metallic, and of any desired transverse as well as longitudinal cross sectional configuration. For example with respect to fragile parts of irregular shape; ferrous work pieces having thin portions and/or edges cannot be clamped securely and will move in magnetic and vacuum chucks; non ferrous work pieces (metallic or non metallic) will also move in said chucks; and securement by adhesion with a cement or the like is costly and many times deleterious to the material of the part to be produced. Therefore, it is an object of this invention to provide means by which any and all work piece materials are reliably secured for machining.
The work pieces involved here are characterized by thin and/or sharp features subject to deformation, when improperly treated. In this respect, strength of the material and its physical properties are to be considered. That is, the material to be machined may be maleable or resilient, soft or hard, and its tensile strength and tendancy to deform will vary. Therefore, crushing, bending and stretching are to be taken into consideration, it being an object of this invention to preclude any deforming or adverse effect from bending and stretching. However, it is an object of this invention to advantageously employ forming, bending and stretching, as and when circumstances require.
It is an object of this invention to accomodate the accepted methods of material removal as practiced in the machining arts, and for example cutting tools as they are used in lathes and milling machines and the like of all types are to be used. Chemical milling and electrical discharge milling, and all associated means and methods of tool feeds and control are to be employed as may be required. With this invention, the work piece is pulled tightly over a curved support which is traversed by the cutting tool for the removal of material therefrom. Accordingly, it is an object of this invention to provide anchor means and also tensioning means to secure the work piece tightly to the curved support. In practice, the arcuate support is the circumferential curvature of a wheel turned as by a lathe, but this embodiment is not to preclude other curved supports such as those which may be placed upon or associated with conventional milling machines and the like. It is still another object of this invention to advantageously employ the aforesaid tensioning means to stretch materials that will work harden and thereby take a set configuration established by the curved support surface.
The present invention is characterized by the curved supporting surface that positions the work piece under tension. In practice, the work piece is elongated and extends between an anchor means and a tensioning means. And a feature is control over the tension applied to the work piece. Accordingly, it is an object of this invention to provide tension control means by which the work piece is held tightly to the curved support. For work pieces which are to retain their original straight condition, the tension applied is controlled so as not to exceed the yield point of the material. However, for work pieces which are to acquire the form of the curved support, the tension applied is controlled for dynamic movement wherein the yield point of the material is exceeded so as to stretch and set the same. It is to be understood that the support surface is not to be limited to a true arc, but may also be any curvilinear surface.
It is an object of this invention to provide for variations in part contour, both transversely and longitudinally. To this end the tool feed means is controlled both transversely and longitudinally with respect to the support surface, so as to cut transverse as well as longitudinal cross sections as required. In the lathe embodiment herein disclosed, the transverse part cross section may involve grooves, shoulders and tapers and the like. And, in said lathe embodiment, a longitudinal tapered part involves eccentric turning and the like. For example, the arcuate or curvilinear surface will have offset curvatures as required, or the tool feed control means will vary the cutting positions of the tool, as may be required. Position of the cutting tool will be computer or tape controlled, so as to be varied or interrupted as required.